/*******************************************\
  Base64函数不是原创，这边只是改成类的形式，
  方便 DronFw 使用
  This JavaScript was writen by Dron.
  @2003-2008 Ucren.com All rights reserved.
\*******************************************/
DronFw.Class.Base64 = function ()
{
	var keyStr = "ABCDEFGHIJKLMNOP" +
				"QRSTUVWXYZabcdef" +
				"ghijklmnopqrstuv" +
				"wxyz0123456789+/" +
				"=";

	this.encode = function (input) {
	  input = escape(input);
	  var output = "";
	  var chr1, chr2, chr3 = "";
	  var enc1, enc2, enc3, enc4 = "";
	  var i = 0;

	  do {
		 chr1 = input.charCodeAt(i++);
		 chr2 = input.charCodeAt(i++);
		 chr3 = input.charCodeAt(i++);

		 enc1 = chr1 >> 2;
		 enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
		 enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
		 enc4 = chr3 & 63;

		 if (isNaN(chr2)) {
			enc3 = enc4 = 64;
		 } else if (isNaN(chr3)) {
			enc4 = 64;
		 }

		 output = output + 
			keyStr.charAt(enc1) + 
			keyStr.charAt(enc2) + 
			keyStr.charAt(enc3) + 
			keyStr.charAt(enc4);
		 chr1 = chr2 = chr3 = "";
		 enc1 = enc2 = enc3 = enc4 = "";
	  } while (i < input.length);

	  return output;
	}

	this.decode = function (input) {
	  var output = "";
	  var chr1, chr2, chr3 = "";
	  var enc1, enc2, enc3, enc4 = "";
	  var i = 0;

	  // remove all characters that are not A-Z, a-z, 0-9, +, /, or =
	  var base64test = /[^A-Za-z0-9\+\/\=]/g;
	  if (base64test.exec(input)) {
		 alert("There were invalid base64 characters in the input text.\n" +
			   "Valid base64 characters are A-Z, a-z, 0-9, '+', '/', and '='\n" +
			   "Expect errors in decoding.");
	  }
	  input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");

	  do {
		 enc1 = keyStr.indexOf(input.charAt(i++));
		 enc2 = keyStr.indexOf(input.charAt(i++));
		 enc3 = keyStr.indexOf(input.charAt(i++));
		 enc4 = keyStr.indexOf(input.charAt(i++));

		 chr1 = (enc1 << 2) | (enc2 >> 4);
		 chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
		 chr3 = ((enc3 & 3) << 6) | enc4;

		 output = output + String.fromCharCode(chr1);

		 if (enc3 != 64) {
			output = output + String.fromCharCode(chr2);
		 }
		 if (enc4 != 64) {
			output = output + String.fromCharCode(chr3);
		 }

		 chr1 = chr2 = chr3 = "";
		 enc1 = enc2 = enc3 = enc4 = "";

	  } while (i < input.length);

	  return unescape(output);
	}
}